src/librustc_typeck/coherence/unsafety.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Unsafety checker: every impl either implements a trait defined in this
  12 //! crate or pertains to a type defined in this crate.
  13
  14 use middle::ty;
  15 use rustc_front::visit;
  16 use rustc_front::hir;
  17 use rustc_front::hir::{Item, ItemImpl};
  18
  19 pub fn check(tcx: &ty::ctxt) {
  20     let mut orphan = UnsafetyChecker { tcx: tcx };
  21     visit::walk_crate(&mut orphan, tcx.map.krate());
  22 }
  23
  24 struct UnsafetyChecker<'cx, 'tcx:'cx> {
  25     tcx: &'cx ty::ctxt<'tcx>
  26 }
  27
  28 impl<'cx, 'tcx, 'v> UnsafetyChecker<'cx, 'tcx> {
  29     fn check_unsafety_coherence(&mut self, item: &'v hir::Item,
  30                                 unsafety: hir::Unsafety,
  31                                 polarity: hir::ImplPolarity) {
  32         match self.tcx.impl_trait_ref(self.tcx.map.local_def_id(item.id)) {
  33             None => {
  34                 // Inherent impl.
  35                 match unsafety {
  36                     hir::Unsafety::Normal => { /* OK */ }
  37                     hir::Unsafety::Unsafe => {
  38                         span_err!(self.tcx.sess, item.span, E0197,
  39                                   "inherent impls cannot be declared as unsafe");
  40                     }
  41                 }
  42             }
  43
  44             Some(trait_ref) => {
  45                 let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id);
  46                 match (trait_def.unsafety, unsafety, polarity) {
  47                     (hir::Unsafety::Unsafe,
  48                      hir::Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
  49                         span_err!(self.tcx.sess, item.span, E0198,
  50                                   "negative implementations are not unsafe");
  51                     }
  52
  53                     (hir::Unsafety::Normal, hir::Unsafety::Unsafe, _) => {
  54                         span_err!(self.tcx.sess, item.span, E0199,
  55                                   "implementing the trait `{}` is not unsafe",
  56                                   trait_ref);
  57                     }
  58
  59                     (hir::Unsafety::Unsafe,
  60                      hir::Unsafety::Normal, hir::ImplPolarity::Positive) => {
  61                         span_err!(self.tcx.sess, item.span, E0200,
  62                                   "the trait `{}` requires an `unsafe impl` declaration",
  63                                   trait_ref);
  64                     }
  65
  66                     (hir::Unsafety::Unsafe,
  67                      hir::Unsafety::Normal, hir::ImplPolarity::Negative) |
  68                     (hir::Unsafety::Unsafe,
  69                      hir::Unsafety::Unsafe, hir::ImplPolarity::Positive) |
  70                     (hir::Unsafety::Normal, hir::Unsafety::Normal, _) => {
  71                         /* OK */
  72                     }
  73                 }
  74             }
  75         }
  76     }
  77 }
  78
  79 impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
  80     fn visit_item(&mut self, item: &'v hir::Item) {
  81         match item.node {
  82             hir::ItemDefaultImpl(unsafety, _) => {
  83                 self.check_unsafety_coherence(item, unsafety, hir::ImplPolarity::Positive);
  84             }
  85             hir::ItemImpl(unsafety, polarity, _, _, _, _) => {
  86                 self.check_unsafety_coherence(item, unsafety, polarity);
  87             }
  88             _ => { }
  89         }
  90
  91         visit::walk_item(self, item);
  92     }
  93 }